08-10 SS Turbocharged General Discussion Discuss the 2008 - 2009 Chevy Cobalt SS Turbocharged. On sale since the second quarter of 2008.

Bnr k04-gt28

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Old 12-08-2010, 10:47 PM
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What kind of Trq numbers do you think we will see with this thing? Will that decrease with this sized turbo? I personally like to have more trq than HP.
Old 12-09-2010, 03:34 AM
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im opposate. id rather have more hp than torque, and just raise the redline a bit. i personally think a car with 400whp and 350 tq shifting at 8k will pull a car with 400whp and 450 tq shifting at 6.5k with the same gearing. plus its easier on the clutch and drivetrain.
Old 12-09-2010, 04:35 AM
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Impulse Engines : Performance : More Average Torque

Do the math that my link shows you with your current dyno numbers and tell me what you get.



And I would guess that in your example the 400whp 450wtrq would win as that Trq would help accelerate you faster from a dig. Sorry don't do rolls.
Old 12-14-2010, 09:48 AM
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bump for updates
Old 12-14-2010, 12:02 PM
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woke up this morning wondering the same thing^^^^
Old 12-14-2010, 12:10 PM
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Well, here's something to hold us over that BNR sent, courtesy of Cubaniche:

Stage 1 (K04-GT2860)



Stage2 (K04-GT2871)

Old 12-14-2010, 12:42 PM
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Those graphs look exactly like the regular gt28 graphs that can be found floating around. Idk if that is the exact graph for this combo. I was expecting a little loss in efficiency. If this thing can flow 45lbs/min ill be happy
Old 12-14-2010, 12:51 PM
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Thats the same thought Stamina and I had. I asked BNR for the graphs directly and thats what he sent. Seems to me hes pretty confident that his mods will flow almost the same...???
Old 12-14-2010, 03:37 PM
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how does our K04 hotside compare to a 2871?
Old 12-14-2010, 04:15 PM
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Originally Posted by RoadconeTuning
how does our K04 hotside compare to a 2871?
It doesn't...

But in all seriousness, here's the info...

Old 12-14-2010, 05:34 PM
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wow, i'll be surprised if the 2871 makes over 400
Old 12-14-2010, 06:15 PM
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Originally Posted by RoadconeTuning
wow, i'll be surprised if the 2871 makes over 400
You're saying that based on the turbine?
Old 12-15-2010, 08:56 AM
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I'd love to be wrong here but, I just dont think its going to work as well as everyone thinks... Full-Race has a T3-T67 hybrid that is okay but my buddy swapped to a GT4088 which has a few mm smaller compressor and picked up like 50hp on pump gas lol
Old 12-15-2010, 10:24 AM
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Originally Posted by RoadconeTuning
I'd love to be wrong here but, I just dont think its going to work as well as everyone thinks... Full-Race has a T3-T67 hybrid that is okay but my buddy swapped to a GT4088 which has a few mm smaller compressor and picked up like 50hp on pump gas lol
I pulled up the turbine specs. Were you wanting the compressor wheel specs? I'm not sure I follow what you mean as far as just looking at the turbine end of the turbo.

Here are the compressor specs:

Old 12-15-2010, 10:55 AM
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the 2871 will make over 400 horsepower... the 2860 will make 370hp
Old 12-15-2010, 11:33 AM
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i wouldn't see our exhaust side killing flow that much.. and a 2871 turbo on the stock manifold has already made 400+ whp
Old 12-15-2010, 11:37 AM
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i think low 400s are a respect amount of power for a pretty much stock turbo
Old 12-15-2010, 11:38 AM
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Well, the thing is that he has also machined the exhaust side, so it no longer has the stock specs/dimensions and is basically an unknown now.
Old 12-15-2010, 11:41 AM
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well i can't wait for Joe to get his so we can get it on the dyno
Old 12-15-2010, 12:24 PM
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Originally Posted by Stamina
Well, the thing is that he has also machined the exhaust side, so it no longer has the stock specs/dimensions and is basically an unknown now.
Exactly. People are making assumptions off of what a regular 2871r would make.
Old 12-15-2010, 12:51 PM
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correct me if im wrong but is this not just a wheel/cover swap on the compressor side? I was saying stock K04 turbine w/ a 2871 compressor just doesnt seem like it would work all that well... bigger heavier wheel trying to grab more air and keeping the same force on the turbine when the 2871 clearly has a bigger area for the exhaust to apply its force... now if hes stuffing a 2871 into a stock turbine HOUSING then this could be veeerrryyy interesting

Last edited by RoadconeTuning; 12-15-2010 at 01:02 PM.
Old 12-15-2010, 01:00 PM
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Originally Posted by RoadconeTuning
correct me if im wrong but is this not just a wheel/cover swap on the compressor side?
Its a full gt28 conversion. Both wheels are replaced and the housing on both sides are machined accordingly to fit. This is why I guess he feels comfortable using the stock garrett gt28 flow maps, because it will flow very similarly. Its not JUST a big wheel upgrade. Again, machined K04 housing with full gt2860 and gt2871 internals.
Old 12-15-2010, 01:04 PM
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Originally Posted by cubaniche
Its a full gt28 conversion. Both wheels are replaced and the housing on both sides are machined accordingly to fit. This is why I guess he feels comfortable using the stock garrett gt28 flow maps, because it will flow very similarly. Its not JUST a big wheel upgrade. Again, machined K04 housing with full gt2860 and gt2871 internals.
On the 2871 the compressor cover is the actual 2871 cover. The only machining done was for the shaft and turbine to fit the K04 turbine housing/center. Right?
Old 12-15-2010, 01:04 PM
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that will work pretty phenomenally then...
Old 12-15-2010, 01:43 PM
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Originally Posted by 09BlueBaltSS
On the 2871 the compressor cover is the actual 2871 cover. The only machining done was for the shaft and turbine to fit the K04 turbine housing/center. Right?
Correct. The 2871 has the upgraded housing. I was trying to minimilize what I was trying to say, sorry. I would love the 2871 but the upgraded housing eliminates the BPV and thus would require a BOV somewhere in the system and, me personally, I dont wanna mess with all that..lol...I think the 2860 should get us to at least 350 conservatively and 370 pushing it. Im happy with that, plus maybe the ZZP cams if they ever get released

Last edited by cubaniche; 12-15-2010 at 01:49 PM.


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